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Of course if you head out to the desert don't forget a good idle test.
It will be interesting to see how the results play out.
 

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Discussion Starter · #43 ·
Update:

Finished building the project box for the Arduino board. No more clip leads & worries about sudden stops or corners or nuthin'.

Electronic engineering Electronics Circuit prototyping Circuit component Microcontroller


Electronic device Adapter Technology Product Electronics accessory


Product Electronic device Technology Electronics accessory Cable


Test run this morning with the new plug and play set up gathered a bit more data on a 20 minute run. This time, I ran the Torque App, logging OBD engine coolant and air intake.

Chart and numbers at the conclusion of the run below.

Line Map Text Ecoregion Slope

Text Blue Font Line Number


Notes:
Referring to line 177, observe column D header "OTW/Trans" is the output from transmission to the "oil-to-water" heat exchanger buried in engine coolant at the bottom of the engine rad. Fluid leaving trans is 114.46.

Now observe column E header "OTA/OTW". This is the line connecting the "oil-to-water" exchanger to the "oil-to-air" exchanger. In this example, fluid leaving the OTW is HOTTER than fluid leaving the trans. Meaning, engine coolant is warming up trans fluid.

Now observe column F header "OTA/Trans". This is the line connecting OTA to trans. In this example, the fluid passed to OTA from OTW is COOLED to 95 before returning to the transmission.

More data coming. Next time, mountains, snow, bears and zombies will be thrown in the mix.
 

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I was doing some research on in-line transmission filters.
I started watching many video reviews and they all showed adding the external filter after the OTA cooler and before the transmission.
Many makes and models and they all said this area was before the oil returned to the transmission.
 

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Discussion Starter · #45 · (Edited)
In attempt to combine mountain climb & descent with exposure to cold, made a run up to the San Bernardino mountains yesterday. Weather forecast snow, so it seemed like a good time.

Unfortunately, weather didn't cooperate with NOAA. And it seemed like every Southern California resident with rubber and fuel had plans to be in the Big Bear area too.

Traffic was absurd towards the top of the mountain, coming to a complete stop right around 6,000 ft mark @ the intersection of 330 & 18. So grabbed the 18 and ran over to Lake Arrowhead, then back down the mountain to San Bernardino.

With the drive train at full operating temp, turned on logging @ 330 & 210, elevation 1,318 above sea level, made the 35 minutes run to 6.040 ft @ Running Springs. The 15 mile climb to 4,700 ft @ "normal" speed of a comfortable drive up the serious switchbacks. Not too fast, not slow. 06 was loaded with 2 passengers and regular junk people carry, just like every other day of the week. Ambient temp at the bottom of the hill 65, 50 @ Running Springs.

Bar chart of the last few temp samples before turning off logging.
Text Line Parallel Font Pattern


Nice slow cruise over to Lake Arrowhead. Stop for coffee and quick tour of the village, then back down the hill, descending from 5,500 ft to 840 ft. 25 minute run 17 miles. No D3 use of engine braking, just occasional tap on the brakes where needed.
Blue Text Line Diagram Font


So there you go, an average RL under moderate strain climbing a mountain in mild weather. That same RL coasting down a mountain.

Now, a storm has hit the So Cal area and its snowing like mad up there. Bummer that. It's not too unusual for snow to get down to the 3K ft level so there should be opportunity soon in the local mountains. Perhaps Mount Palomar or the Cuyamaca's. When that happens, an overnight stay in a cabin would facilitate a nice cold start scenario.

Thermal management #'s converted to % of influence in the chan.

Text Font Line Number
 

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Data is relatively simple to understand now, charts are still a PITA, to read, but maybe that's my 3yo iPad 2 tablet and the screen resolution.

Keep up the good work, Six!!!
 

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Discussion Starter · #47 · (Edited)
Data is relatively simple to understand now, charts are still a PITA, to read, but maybe that's my 3yo iPad 2 tablet and the screen resolution.

Keep up the good work, Six!!!
Thanks Mak. Since we got hit with that huge storm last night, it got down right cool around here. Actually had to wear socks, shoes, long pants and everything.

Now that the Arduino board is safely contained in a box, setting up for logging is painless. This is what's happening under the hood @ start up on a 42 degree morning, idling in the driveway for 8 unnatural minutes, trans in neutral, HVAC set LO:

Line Text Parallel


Low/high values used to create graph above

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At the 8 minute mark, logging was turned off, data captured and saved. So, in the data set below start temps are higher than stop temps in the data above - only cuz of 3 additional minutes idle time while data was captured and loaded to a temp file.

Text Line Diagram Parallel Plot


Low/high values used to create graph above

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Even with a clear understanding of WHAT the OTW & OTA are doing in fluid flow, direction and thermal influence, WHY the OTW exists remains unexplained on the OEM side of the industry. SAE doesn't explain its purpose - at least not in public information I've seen. And Honda's FSM only adds to the mystery through odd syntax and reference to none existent components (like an external trans filter!).

So the door open to speculation remains open - which is what was to be avoided by this little project.

As long as speculation is on the table, I'll speculate the OTW exists for the singular purpose of incremental improvement to the almighty MPG prominently displayed on window stickers. Perhaps there is information to the contrary - perhaps service life is increased by X% through this thermal management design implemented by so many OEMs - but I doubt that is the real goal.

OEM's need that CAFE # - and to get it - they'll concoct designs that allow incompatible fluids to mix.
 

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I wonder what temps would be seen leaving the trans under long heavy towing conditions.
Then the OTW cooler might actually aid in the cooling process, possible?
 

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Discussion Starter · #49 · (Edited)
I wonder what temps would be seen leaving the trans under long heavy towing conditions.
Then the OTW cooler might actually aid in the cooling process, possible?
Basing what I've seen in other vehicles, fluid temps above 220 are pretty common, so YES, there might be times under stress where the OTW serves as an intermediate cooling element before passing to OTA.

Among the many interesting things to come from looking into Honda's OTW implementation, is the thermal exchange capacity of such a small component and such a tiny amount of fluid forced thru iddy biddy veins. It's influence is remarkable.
 

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Yes, the OTW exchanger is there to ensure that ATF temperatures do not climb above a certain level. ATF temperature, to my understanding, is pretty immaterial to durability at the temperature range you saw. That is, whether ATF is 120 deg F or 180 deg F doesn't really matter. What matters is when the ATF sump temperature wants to climb to 250-300 deg F or above, obviously under severe conditions. If sump temperatures are that high, you know the fluid temperature INSIDE the wet clutches and other components will be even higher. That's when you see a lot of fluid degredation, damage to clutches, etc. So the OTW exchanger is there to try to put a ceiling on ATF temperature. That ceiling will, at least in theory, be the engine coolant temperature.

Every automatic transmission has a OTW exchanger of some kind. Traditionally, that has been in the radiator. I was working on a 2012 Civic this weekend and noticed its exchanger was a small stand-alone unit over by the transmission, with two small rubber lines conveying coolant to and from this unit.

In applications where towing is anticipated, an OTA exchanger is often supplemented, and run in series with the OTW exchanger. There could, in theory, be a situation where the transmission is feeding the OTW exchanger 300 deg F fluid, and that OTW exchanger can cool it down to only 250 deg F (for instance). In this case, the OTA exchanger works in series to cool it down even more. As you've demonstrated, OhSix, the OTA exchanger really isn't needed in most cases. In fact, you could say that it's "over-cooling" the fluid in most cases. You could argue that if the fluid were 50 degrees warmer, you'd have a bit less drag and a bit better economy. But if you took the OTA exchanger out, you'd lose that extra capacity for severe conditions. I guess one option would be to have the OTA exchanger thermostatically-controlled, but that'd add a lot of complexity to the system.

I think you've proven that the ATF cooling system on these is pretty over-engineered for most situations.
 

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Discussion Starter · #51 · (Edited)
Agree with your conclusions Hokie. In terms of absolute accuracy, the temp probe system in use here is limited by virtue of surface mounted/contact sensors vs. sensors sunk in fluid. If I've interpreted the FSM correctly, the factory trans temp probe is sunk in pan fluid - which itself is "inaccurate" due to its physical location. Temps inside clutch assemblies would be much higher than fluid anywhere else in the system. In this regard, absolute temp accuracy is unavailable anywhere - and probably non-critical in the world of engineering averages.

To that point: engine coolant probes in this system routinely report much lower temps than the single factory probe sunk in fluid. At the highest measured values, OBD engine coolant reported 205 while the surface mounted probe @ the block "send" hose reported 189 - the delta between those temps is the result of surface vs sunk sensors and actual sensor location. Knowing the system is not capable of hyper-accurate temp measurements, the most important function is seeing deltas between each probe location. If one were more anal than I, factoring in coupling loss of surface probes could be calculated and formulas built to more closely reflect the actual temp of fluid in the hoses. But I'm at the end of my geek rope - and besides - "normalizing" data can be controversial.

One of the new-to-me results from the project is OTW is not a "pre-heater". At least not in way I understood that notion (which was to warm very cold fluid on its way into the trans for the purpose of improving service life) - and certainly not in the the drive scenarios measured so far. Even in extreme cold conditions, if OTW were serving to raise fluid temps in the first few minutes of driving with a warm engine, OTA knocks that temp down by a predictable % influenced by outside air temp / flow.

What surprises me most is the effect OTW has on trans fluid temps. What I mean is, the very small volume of fluid moving thru the exchanger has drastic influence on temps. I can see how under fully loaded, extreme terrain conditions, OTW would bring trans temps closer to engine coolant, giving OTA a chance to drop it further before re-entering the trans.

The sum total of OTW's presence seems to be establishing an (as close as possible) average temp over the very long term in the widest array of environmental and load conditions. Perhaps I'm stuck in a mental model here, but... IF cold trans fluid = long service life, OTW's job comes down to influencing fluid viscosity. And that influence is less about service life / more about the overall goal of mechanical/rotational drag leading to VERY small increases in fuel economy - which when averaged out over millions of vehicles increases CAFE. For the good of the planet - of course. But that's pure speculation on my part.

Pre-summer desert season is coming up - a bunch of river rat/dune running junkie buddies take maximum advantage of spring with weekend runs out to Buttercup and Glamis. Between San Diego and Imperial valley is the Cleveland National Forrest - lots of long uphill pulls & mountain terrain to travel before dropping to the valley floor. That'll be a good time to drag a buggy trailer out and log a few new drive scenarios.

Maybe even give 06 a chance to tackle a dune or two? NAH! That sand is WAY too soft.
 

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Liquid-to-liquid heat exchangers are very effective -- moreso than liquid-to-air exchangers. I agree with you: it's remarkable the influence that OTW exchanger has on the ATF temperature. I think this is why it's ~generally~ not recommended to go with an air exchanger only, and take the liquid exchanger out of the scenario. It'd probably be okay in most circumstances, but there may also be times where the relatively small OTA exchanger cannot keep up with the heat input from the transmission. Such may be the case in times of idling around town, where you may not be using the A/C (so the cooling fans wouldn't be turning), but you may have high transmission temperatures due to lots of shifting or low speed movements. You might begin to build heat into the ATF that an OTA exchanger alone cannot remove -- especially if there's no air moving across it. The benefit of the OTW cooler is that it's always got fluid moving across it (coolant), and it's relatively "cool" coolant as well, being at the bottom of the tank.

I thank you, again, for your tireless work on gathering this data. It removes all conjecture and speculation. The transmission cooling system on these is well engineered, and has more capacity than most of us will ever reach.
 

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Great work OhSix!

I wonder at what temp the AT temp light comes one?
 

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Great work OhSix!

I wonder at what temp the AT temp light comes one?
I've had my electric sender needle gauge as high as 230 and the dash light has never come on. Some context is that the sender is mounted in a Derale spin off filter mount that is on the output side of the pan about 10 inches of hose away. I can't speak for specific accuracy expect that I've used a better than average IR temp reader to compare the pan, oil filter can and gauge and that they were all remarkably consistent. My whole intention was that if I ever had the light come on atleast I'd have a gauge point of reference, but all in all using my IR temp reader, the guage seems pretty accurate at displaying the output at
the pan.
 

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Good summary, OhSix!

The OTW exchanger most definitely IS a pre-heater! That the OTA cooler eliminates some of that heat is true, yet consider: The OTA cooler will, in most climates, cool the fluid the majority of the time. The OTW exchanger raises the start temp from which that cooling begins. So, OTW is still a very effective pre-heater.

It would be ideal if the OTA cooler had a thermostat that allowed the fluid to bypass it until it reached a sufficiently high temp so as to 'need' the auxiliary cooling it affords. However, that adds cost and complexity that is likely not deemed necessary or useful for this kind of application.

And you're absolutely right that the pre-heating is for mpg/CAFE reasons. Too, Honda places a lot of emphasis, including marketing efforts, on a certain ideology that is to do with not just efficiency, but relatively low usage or consumption of 'stuff' (fuel, oil, maintenance items, and so forth). There are many, MANY SAE papers and other technical publications dealing with ways to eke out _very_ small increases in mpg. GM has been doing it on a large scale for perhaps the longest time of the majors in North America.

Again, very well done, and thanks!
 

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Discussion Starter · #56 ·
Thanks for the comments. Its always good to have eyes on this stuff.

Found an overlooked file on the desk top that should have been included with data posted after last weekends run. Basically, the trek up SR 330 to Big Bear was interrupted by crazy traffic, so the trip was diverted to Arrowhead. After sitting in traffic for a brief time, 06 momentarily diverted to a mountain road pull out. Logging was stopped, data saved up to that point, then restarted as 06 rejoined the stop and go traffic.

What makes this interesting is it reflects negotiating traffic (meaning moving slowly) - after a 90 mile freeway drive followed by a climb from ~1,300 to ~5,500 ft.

A mountain jam, so to speak.

The road up:
Map Trail Geology Fault Geological phenomenon


This is approximately where traffic got crazy and the trip diverted towards Arrowhead.

Map Rock Organism Tree Geology


~ 28 minutes in traffic to travel 2 miles. No fun, even with nice scenery.

This is how temps mapped out. Hope this resolution is useable.

Text Line Font Parallel Design
 

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Great work OhSix!

I wonder at what temp the AT temp light comes one?

That may be determined this year, as possibly the temp at which the "D" blinks...
 

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I think that last chart further demonstrates the point of the OTW exchanger. Whether it acts as "pre-heater" or a "cooler" depends entirely on the transmission output temperature. If the ATF temperature is lower than the coolant temperature (as it often is), then the OTW exchanger will transfer heat from the coolant to the ATF. If the ATF temperature is higher than the coolant temperature, then the OTW exchanger will transfer heat from the ATF to the coolant.

You can see that during the last third of that graph, the transmission output temperature began to rise. But the coolant temperature didn't change, and the OTW-to-OTA temperature was also roughly consistent. If you continued on this trend of stop-and-go traffic climbing up a mountain, the transmission output temperature would likely climb higher than the coolant temperature, and the OTW exchanger would actually cool the ATF.

And just imagine things without the OTA exchanger. Transmission input temperatures were in the 120-130 deg F range. Transmission output temperatures were in the 170-180 deg F range, so it's adding about 50 deg F to the ATF temperature. If your OTA exchanger was not there (as with most vehicles), the transmission's input temperature would essentially be the OTW-to-OTA temperature point...about 180 deg F. The transmission's still going to add 50 deg F to that by doing what it does. Without the OTA exchanger, your Trans-to-OTW temperatures would likely be in the 230 deg F range. In this case, the OTW exchanger would definitely be serving as a cooler!
 

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Discussion Starter · #59 · (Edited)
Spot on Hokie. The trends seen so far speak to the value of averages accrued from many, many samples over every conceivable scenario, which is what design engineering solves for - and why auto OEM employ torture tests.

At this point, I think we have a basic understanding how the system works when the RL is tasked with being a passenger vehicle. Which is to say, the transmissions thermal control system is very well implemented.

When the trans is challenged with weight and rolling resistance of mountain & varied terrain, I expect to see the trans/OTW trend line shoot well above engine coolant lines where it will be reduced by OTW then further reduced by OTA.

As a former proponent of eliminating OTW in favor of eliminating potential for SMOD - an opinion which was based solely on a personal urban legend, I've inverted.

Now, if there was a permanent/cost effective solution for SMOD, we'd be in excellent shape. IMO: it's a grotesque error to design a system that would allow incompatible fluids to mix under any conditions, especially in light of SMOD events occurring during & after warranty with no reliable, readily identifiable evidence of pending doom. But that's just me being a butt head with an opinion.

Speaking of eliminating potential for SMOD, I'm more curious than ever about the Spectra rad - torn down in this thread. Given its robust mechanical OTW mounting design it clearly wins in the category of fluid isolation, BUT, it's OTW concentric design combined with fewer/wider radiator passageways, its heat management effectiveness is a big question mark.

Anyone want to take a brand new OSC off my hands? I'd be willing to swap it for a Spectra just to get measurements! :act010:

EDIT comment: IMO & reiterating Hokie's & bulwnkl's comments: the most accurate description of OTW is "heat exchanger". Its role is to both raise and lower trans fluid temps, depending on conditions. That role gets back to averaging temperature control over long term use - which is something not seen in data samples so far.
 

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I think heat exchanger is how it's been commonly referred to in past discussions as well. Only now we have a much better idea of exactly what it does.

Perhaps other terms that could be used are a temperature normalizer or conditioner.

Regardless, it seems to be a bad idea to bypass the exchanger in an attempt to mitigate the SMOD issue.
 
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